Optical communication systems have many advantages over communication systems that transmit electrical signals. For one, electrical signals are susceptible to electromagnetic noise whereby great care must be taken to shield those signals from sources of electromagnetic radiation. On the other hand, optical signals are relatively immune to electromagnetic radiation and can be easily shielded during transmission. Additionally, electrical signals can be transmitted for only relatively small distances since they incur losses proportional to the square of the distance. Optical signals, on the other hand, can be transmitted for great distances with little or no loss. For these and other reasons, many communications systems incorporate optical signals.
Optical communication systems are rather limited in transmitting radio frequency (RF) signals and other analog signals encoded with a high degree of information. Optical communication systems have a limited spurious-free dynamic range (SFDR). A relatively low SFDR, in turn, requires that the communication signals be at a relatively high optical signal to noise level.
As a practical matter, the relatively low SFDR of optical communication systems limits where the benefits of an optical communication can be reaped. As one example, optical communication systems are used in conjunction with wireless networks. The optical communication system may carry signals between switches within the network and/or from a base station up to the antenna in a tower. The optical communication system in this example transmits the signals over an optical fiber in order to achieve the advantages of low losses and low susceptibility to noise. These wireless networks must perform a great deal of processing of the electrical signals detected at the tower before they can be converted into optical signals and transmitted over a fiber to a remote location. As noted above, the optical communication system has a relatively low SFDR and cannot directly receive RF signals having a low optical signal to noise level. Consequently, the RF signals may be need to be converted into digital signals or undergo extensive filtering and amplification before they are converted into optical signals. This processing adds a cost to the network which may render it impractical to implement an optical communication system.